use pregenerated CRC32 lookup tables for retain on Win32 and GNU/Linux

This code could be possible reused on low-end targets with limited RAM.

code to generate lookup table:
[---------------------------------------------------------------------]

/* CRC lookup table and initial state. */
uint32_t crc32_table[256];

/* Generate CRC32 lookup table. */
void GenerateCRC32Table(void)
{
unsigned int i, j;
/* Use CRC-32-IEEE 802.3 polynomial 0x04C11DB7 (bit reflected). */
uint32_t poly = 0xEDB88320;

for (i = 0; i <= 0xFF; i++)
{
uint32_t c = i;
for (j = 0 ; j < 8 ; j++)
c = (c & 1) ? (c >> 1 ) ^ poly : (c >> 1);
crc32_table[i] = c;
}
}

void main(void)
{
GenerateCRC32Table();
int j=0;
for(int i=0; i<256; i++) {
printf("0x%08X, ", crc32_table[i]);
if (++j >= 8) {
j = 0;
printf("\n");
}
}
}
[---------------------------------------------------------------------]

#!/usr/bin/env python
# -*- coding: utf-8 -*-
# This file is part of Beremiz.
# See COPYING file for copyrights details.

from __future__ import absolute_import
from plcopen.XSLTModelQuery import XSLTModelQuery


class InstancesPathCollector(XSLTModelQuery):
    """ object for collecting instances path list"""
    def __init__(self, controller):
        self.Instances = []
        XSLTModelQuery.__init__(self,
                                controller,
                                "instances_path.xslt",
                                [("AddInstance", self.AddInstance)])

    def AddInstance(self, context, *args):
        self.Instances.append(args[0][0])

    def Collect(self, root, name, debug):
        self._process_xslt(root, debug, instance_type=name)
        res = self.Instances
        self.Instances = []
        return res